Method of drilling

ABSTRACT

A composition and method for preventing catastrophic vibration of a drill string during slim hole drilling wherein there is employed an additive composed of sulfurized lard oil, mineral oil, and halogenated paraffin.

ilnite States Patent 11 1 1111 3,712,393 Sheldahl et al. 1 Jan. 23, 197354 METHOD OF DRILLING 3,214,374 1'o/l9ss slmfieii .I .Liffiiiffi3,372,112 3/1968 Parker Inventors! D393 i-d lidi z 399 2 3 1N; 3,635,2941/1972 Faulk etal ..l75/65 46319; 161111 11. Striegler, Richardson, Tex.75080 Primary ExaminerDavid H. Brown Att -Blh S.Th dRd'kW.M-

[73] Assignee: Atlantic Richfield C0., New York, 32 uc er arp an o encac [22] Filed: Jan. 20, 1971 21 Appl. No.: 108,170

57 ABSTRACT A A composition and method for preventing catastrophicvibration of a drill string during slim hole drilling wherein there isemployed an additive com- [52] U.S. Cl ..l75/65, 252/85 C, 252/85 P [51]Int. Cl. ..E2lb 21/04 [58] Field of Search 755}/6g;% posed of sulfurizedlard oil, mineral oil, and

' halogenated paraffin.

[56] References Cited UNITED STATES PATENTS 9 Claims, No Drawing; I

2,773,030 12/1956 Tailleur ..252/8.5P

METHOD OF DRILLING BACKGROUND OF THE INVENTION Heretofore in rotarydrilling a wellbore in the earth, the drilling bit and the drill string(drill pipe and drill collars) which supports the bit in the wellboreare both conventionally rotated at rates of from about 100 to about 250rpm. Such drilling rigs, in the petroleum industry, generally drillboreholes having diameters of from about 8% to about 13% inches. Becauseof the drilling of deeper and deeper wellbores, etc. there is a need fordrilling fluids of improved lubricity.

As an exploratory tool, it can be desirable to employ what is known as aslim hole drilling technique wherein the borehole has a diameter of upto about 6 inches, preferably from about 2 to about inches. With slimhole drilling it is desirable to use higher than conventional rotationrates for the bit. For example, rotation rates of at least 400 rpm andas high as 3000 rpm are desirably employed to achieve shorter drillingtime.

By drilling small diameter boreholes with high rotation speeds, largernumbers of exploratory wells can be drilled more economically. Inaddition, the rig used is lighter thereby allowing for more economicalmovement of the rig from one drilling location to another, particularlyinaccessible locations.

However, an omnipresent problem with the high rotation rates in a smalldiameter borehole has been what is termed catastrophic vibration of thedrill pipe. At rotation rates of greater than 400 rpm the drill pipetends to bounce from one side of the borehole to the other at a fasterand faster rate until catastrophic transverse vibration sets in andresults in failure of the drill pipe, usually by twisting off onesection of drill pipe from an adjacent section of drill pipe at theircoupling joint.

Thus, slim hole drilling using the most economical rotation rate for thedrilling bit and pipe is not feasible unless catastrophic vibrationduring drilling is avoided.

SUMMARY OF THE INVENTION It has now been found that improved drillingfluid lubricity is obtained and that catastrophic vibration during highspeed rotation can be prevented by the use of a composition consistingessentially of sulfurized lard oil, mineral oil, and halogenatedparaffin, the composition containing greater than 2 weight percent totalhalogen and greater than 5 weight percent total sulfur. As used herein,weight percent recitations are based upon the total weight of thecomposition unless otherwise specified.

This invention therefore relates to a composition useful in a welldrilling fluid and a rotary drilling method, particularly a slim holedrilling method.

Accordingly, it is an object of this invention to provide a new andimproved composition useful in a drilling fluid to increase thelubricity thereof. It is another object to provide a new and improvedrotary drilling method. It is another object to provide a new andimproved slim hole drilling method.

Other aspects, objects, and advantages of this invention will beapparent to those skilled in the art from this disclosure and theappended claims.

DETAILED DESCRIPTION OF THE INVENTION The lard oil used in thecomposition of this invention can be present in amounts of at leastabout 40, preferably from about 40 to about 80, weight percent, themineral oil in amounts of at least about 10, preferably from about 10 toabout 50, weight percent, and the halogenated paraffin in amounts of atleast about 1, preferably from about 1 to about 20, weight percent.

Substantially any lard oil can be employed in any sulfurization process,a particularly desirable material being that which has a gravity(degrees API) of from about 9.5 to about 12, a viscosity (SUS at 210 F)of from about 360 to about 600, and at least about 10.5 weight percentsulfur based on the weight of the lard oil.

Substantially any mineral oil can be employed, a particularly useful oilbeing that having a gravity (degrees API) of from about 22 to about 25,a saybolt viscosity at F of from about 55 to about 60, and a pour point,F, maximum of about 50.

Substantially any halogenated paraffin can be employed, the paraffincontaining one or more of the halogens, i.e., chlorine, bromine, iodine,and fluorine, preferably chlorine. A particularly suitable material ischlorinated paraffin having a specific gravity (60/60 F) of from about1.16 to about 1.20, from about 40 to about 46 weight percent chlorinebased on the weight of the chlorinated paraffin, a viscosity (SUS at 210F) of from about to about 280, and substantially no free chlorine.

THe composition of this invention can be formed by blending the threecomponents in any desired order with one another at sub-ambient,ambient, or superambient temperatures and pressures until asubstantially homogeneous mixture is obtained. Suitable properties forthe final composition can be a gravity (API) of from about 11.5 to about12.5, a viscosity (SUS at 100 F) of from about 1300 to about 1500, atleast about 5 weight percent, preferably at least about 6 weightpercent, total sulfur, and at least about 3 weight percent, preferablyat least about 3.5 weight percent, total halogen. The maximum amounts ofsulfur and halogen are dictated only by practical considerations such ashow much sulfur the particular lard oil used can be made to pick up inthe particular sulfurization process used.

Other conventional materials can be included in the composition of thisinvention, e. g., corrosion inhibitors, wear inhibitors, oxidationstabilizers, odor stabilizers, and the like. Two or more of thesematerials can be employed as desired.

Corrosion inhibitors can be used in amounts which vary widely butgenerally in an effective corrosion inhibiting amount. These materialsinclude alkali metal sulfonates and alkaline earth metal sulfonates suchas sodium sulfonate and calcium sulfonate, particularly overbasedcalcium sulfonate. Efiective wear inhibiting amounts of at least one ofmonothiophosphates and polythiophosphates (2 to 10 sulfuratons) of zinc,cadmium, tin, iron, cobalt, nickel, vanadium, chromium, manganese,molybdenum, tungsten, titanium, and zirconium, can be employed,particularly zinc dithiophosphate. These additives can each be employedin an amount of from about 1 to about 30 weight percent and can beincorporated before, during, or after mixing of the other components.

The composition of this invention is normally employed in the drillingfluid utilized in the drilling operation. lt has been found that whethera drilling fluid is susceptible to catastrophic vibration during highspeed rotation is related to the scar width value obtained by subjectingthe drilling fluid to a scar width test as hereinafter defined. Thesmaller the scar width, the greater the lubricity of the drilling fluidand, therefore, the less there is of a likelihood of catastrophicvibration while utilizing the drilling fluid in a high speed operation.Thus, the more the scar width value of a given drilling fluid can bedecreased, the more likely it is that a drilling operation can becarried out with that drilling fluid without encountering catastrophicvibration.

The composition of this invention, when added to a drilling fluid, be ita water base (salt water or fresh water) or an oil base or invertdrilling fluid, can substantially reduce the scar width value of thedrilling fluid below the scar width value of that drilling fluid when itdoes not contain the composition of this invention. Generally, thecomposition of this invention is employed in the drilling fluid in anamount effective to substantially reduce the scar width value of thedrilling fluid and generally the scar width value is reduced by at leastabout 0.01 of an inch. This is a substantial decrease in scar width andindicates a substantial increase in lubricity and an ability to preventcatastrophic vibration of drill pipe during high speed rotation,particularly in a small diameter wellbore.

Depending upon the particular drilling apparatus employed, the method ofoperating that apparatus, the composition of the drilling fluid, thesize and depth of the wellbore, and the like, the amount of compositionof this invention which is employed will vary widely. Generally, atleast about 0.1, preferably from about 0.2 to about 10, weight percentof the composition is employed in the drilling fluid and can beincorporated in the drilling fluid by mixing at sub-ambient, ambient, orsuper-ambient conditions of temperature and pressure until asubstantially homogeneous mixture is obtained.

A scar width value for drilling fluid is obtained using an EP Mud Testermodel 211 which is available commercially from the Baroid Division ofthe National Lead Company. This tester is designed to measure thelubricating properties of drilling fluids by mounting a hardened steeltest cup (Rockwell C scale hardness of 58-62) on a rotating shaft andforcing a steel wear block (Rockwell C scale hardness of 58-62) againstthe test cup with a predetermined load while the test cup and wear blockare immersed in the drilling fluid being tested. The load is appliedwith a torque am that is operatively connected to the wear block, thetorque arm containing a torque gauge calibrated in inch pounds. Thefriction load is read on an ammeter scale indicating the electricalcurrent consumption of the driving motor. The motor is run at 1400 rpmwhich amounts to a surface velocity of the test cup of 507 feet perminute, the test cup diameter being 1.378 inches. Each test cup is usedonly once and a fresh spot is selected on the wear block for each run.

In the actual test itself, a friction load corresponding to three ampsis applied with the torque arm and the run continued for seconds holdingthe ammeter reading constant by increasing the load applied to thetorque arm. The width of the scar formed on the wear block by the testcup is then measured and reported in inches. Each test is carried outunder ambient conditions of temperature and pressure using sufficientdrilling fluid to completely immerse the test cup.

It has been found that by employing the composition of this invention inthe manner described hereinabove, substantially smaller scar widths areobtained with a given drilling fluid as compared to scar widths obtainedby the use of commercially available extreme pressure (EP) lubricantadditives.

All of the materials useful in the composition of this invention areavailable commercially and are wellknown in the art and therefore willnot, for sake of brevity, be discussed in detail as to their source ofavailability or method of preparation.

EXAMPLE A composition according to this invention was formed by blending32 weight percent naphthenic mineral oil available commercially asSintex Pale Oil and having the physical properties of API gravity of 22to 25, and saybolt viscosity at F of 55 to 60; 60 weight percentsulfurized lard oil commercially available as Union Base and having thephysical properties API gravity of 9.5 to 11.5, viscosity (SUS at 210 F)of 360 to 450, no less than 10.5 weight percent total sulfur based onthe lard oil; and 8 weight percent chlorinated paraffin commerciallyavailable as Paroil 142 having the properties of specific gravity (GO/60F) of 1.16 to 1.20; 40 to 46 weight percent chlorine based on thechlorinated paraffin, viscosity (SUS at 210 F) of to 280, and no freechlorine. The composition was formed by adding the components in theabove listed order to a blending kettle and mixing same for 1 hour attemperatures in the range of from to F.

A drilling fluid composition was made up by mixing 350 cubic centimeters(350 grams) of distilled water and 14 to 15 grams of bentonite atambient conditions of temperature and pressure until a homogeneousmixture was obtained. The combination of water and bentonite in theabove amounts constituted the volume of drilling fluid employed in eachscar width test for each composition discussed hereinbelow.

Various additives were employed in a separate volume of the abovedrilling fluid by mixing the particular additive with the volume ofdrilling fluid at ambient conditions of temperature and pressure until asubstantially homogeneous mixture was obtained.

The mixture of drilling fluid and additive was then tested for its scarwidth in the manner disclosed hereinabove, keeping the friction loadduring each 20 second test at 3 amps.

1n all 10 runs were made, one run being the drilling fluid with noadditive, 4 runs being the drilling fluid with commercially available HPadditives, and 5 runs being the drilling fluid with additives accordingto this invention. In run 1 the drilling fluid with no additive wasemployed. In runs 2 and 3 different amounts of a commercially availableadditive identified as crude tall oil containing 0.2 weight percentchlorine and 4.4 weight percent sulfur was employed. In runs 3 and 4different amounts of a commercially available additive identified ascoal tar having 1.7 weight percent chlorine and 4.9 weight percentsulfur was employed. Runs 6 and 7 employed different amounts of thecomposition of this invention. Run 8 employed the composition of thisinvention with the addition of 1 weight percent zinc dithiophosphate.Run 9 employed the composition of this invention with the addition ofweight percent sodium sulfonate and 2 weight percent water. Run 10employed the composition of this invention with the addition of weightpercent overbased calcium sulfonate. The results are as shown in thefollowing table:

Scar Width Run Inches 1 Drilling Fluid (D.F.) only 0.16 2 D.F. p us 4 gmcommercial additive 0.04 3 BF. plus 8 gm commercial additive 0.028 4 DP.plus 4 gm commercial additive 0.04 5 BF. plus 8 gm commercial additive0.03 6 DR plus 6 gm invention composition 0.02 7 D.F. plus 3 gminvention composition 0.025 8 D.F. plus 6 gm invention composition lusZn dithiophosphate 0.03

IDF. plus 6 gm invention composition us 1 0 weight Na Sulfonate & 2weight 0.03 water 1? DR plus 6 gm invention composition us verbased Casulfonate 0.025

It can be seen from the above data that the composition of thisinvention decreased the scar width of the drilling fluid even below thatobtained with commercially available additives and therefore increasedthe lubricity of the drilling fluid and also increased the ability ofthe drilling fluid to prevent catastrophic vibration during drillingover what can presently be achieved with commercially availableadditives.

Reasonable variations and modifications are possible within the scope ofthis disclosure without departing from the spirit and scope of thisinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. in a rotary drilling method the improvement comprising employing adrilling fluid containing a composition consisting essentially of atleast about 40 weight percent sulfurized lard oil, at least about 10weight percent mineral oil, and at least about 1 weight percenthalogenated paraffin, said composition containing greater than 2 weightpercent total halogen and greater than 5 weight percent total sulfur,said composition being employed in an amount effective to substantiallyreduce the scar width value of the drilling fluid below the scar widthvalue of the drilling fluid when not containing said composition.

2. A method according to claim 1 wherein said composition has a gravity(APl) of from about 11.5 to about 12.5, a viscosity (SUS at 100 F) offrom about 1300 to about 1500, at least about 5 weight percent totalsulfur, and at least about 3 weight percent total chlorine.

3. A method according to claim 1 wherein there is additionally presentin said composition at least one of (1 an effective rust inhibitingamount of at least one of alkali metal sulfonates and alkaline earthmetal sulfonates, and (2) an effective wear inhibiting amount of atleast one of monoand polythiophosphates of Zn,

Cd Sn, Fe,Co Ni, V, Cr, Mn, Mo,W,Ti and Zr.

4. A method according to claim 1 wherein there IS additionally presentin said composition at least one of Na sulfonate, Ca sulfonate, and Zndithiophosphate, each being present in an amount in the range of fromabout 1 to about 30 weight percent.

5. A method according to claim 1 wherein said drilling method is a slimhole method wherein at least part of the drill string and drill bit arerotated at speeds of from about 400 up to at least about 3000 rpm in asmall diameter wellbore.

6. A method according to claim 1 wherein said amount of said compositionis at least about 0.1 weight percent based on the total weight of saiddrilling fluid.

7. A method according to claim 1 wherein said scar width value isreduced by at least about 0.01 of an inch.

8. A method according to claim 1 wherein said lard oil is present in anamount of from about 40 to about weight percent, said mineral oil ispresent in an amount of from about 10 to about 50 weight percent, andsaid paraffin is chlorinated and is present in an amount of from about 1to about 20 weight percent.

9. A method according to claim 8 wherein said mineral oil is anaphthenic oil which has a gravity (API) of from about 22 to about 25,and a Saybolt viscosity F) of from about 55 to about 60, said lard oilhas a gravity (AP1) of from about 9.5 to about 11.5, a viscosity (SUS at210 F) of from about 360 to about 450, and at least about 10.5 weightpercent sulfur based on the weight of the lard oil, said paraffin ischlorinated and has a specific gravity (60/60 F) of from about 1.16 toabout 1.20, from about 40 to about 46 weight percent chlorine based onthe weight of the chlorinated paraffin, a viscosity (SUS at 210 F) offrom about to about 280, and substantially no free chlorine.

2. A method according to claim 1 wherein said composition has a gravity (*API) of from about 11.5 to about 12.5, a viscosity (SUS at 100* F) of from about 1300 to about 1500, at least about 5 weight percent total sulfur, and at least about 3 weight percent total chlorine.
 3. A method according to claim 1 wherein there is additionally present in said composition at least one of (1) an effective rust inhibiting amount of at least one of alkali metal sulfonates and alkaline earth metal sulfonates, and (2) an effective wear inhibiting amount of at least one of mono- and polythiophosphates of Zn, Cd, Sn, Fe, Co, Ni, V, Cr, Mn, Mo, W, Ti, and Zr.
 4. A method according to claim 1 wherein there is additionally present in said composition at least one of Na sulfonate, Ca sulfonate, and Zn dithiophosphate, each being present in an amount in the range of from about 1 to about 30 weight percent.
 5. A method according to claim 1 wherein said drilling method is a slim hole method wherein at least part of the drill string and drill bit are rotated at speeds of from about 400 up to at least about 3000 rpm in a small diameter wellbore.
 6. A method according to claim 1 wherein said amount of said composition is at least about 0.1 weight percent based on the total weight of said drilling fluid.
 7. A method according to claim 1 wherein said scar width value is reduced by at least about 0.01 of an inch.
 8. A method according to claim 1 wherein said lard oil is present in an amount of from about 40 to about 80 weight percent, said mineral oil is present in an amount of from about 10 to about 50 weight percent, and said paraffin is chlorinated and is present in an amount of from about 1 to about 20 weight percent.
 9. A method according to claim 8 wherein said mineral oil is a naphthenic oil which has a gravity (*API) of from about 22 to about 25, and a Saybolt viscosity (100* F) of from about 55 to about 60, said lard oil has a gravity (*API) of from about 9.5 to about 11.5, a viscosity (SUS at 210* F) of from about 360 to about 450, and at least about 10.5 weight percent sulfur based on the weight of the lard oil, said paraffin is chlorinated and has a specific gravity (60/60* F) of from about 1.16 to about 1.20, from about 40 to about 46 weight percent chlorine based on the weight of the chlorinated paraffin, a viscosity (SUS at 210* F) of from about 150 to about 280, and substantially no free chlorine. 